In recent years internal combustion engine manufacturers have faced the challenge of increasing the power output of engines while also improving fuel economy and reducing emissions. One potential manner of meeting these challenges is the use of Homogeneous Charge Compression Ignition (HCCI) technology. Engines using HCCI technology combine some of the attributes of spark ignition (SI) engines and compression ignition (CI) engines. Like SI engines, the fuel and air within the cylinder is well mixed, which minimizes particulate emissions. Like CI engines, the fuel is ignited by compression, and the engine has no throttling losses, which leads to high efficiency.
A major challenge in the use of HCCI engines is handling the high pressures created within the combustion chamber by the compression of the fuel/air mixture prior to its combustion. These high pressures can place intense strain upon the cylinder head, cylinder liners, pistons and connecting rods of the engine. In addition, operating the engine at such high pressures may decrease the overall efficiency of the engine.
One manner of managing such high pressures within the combustion chamber involves the use of a bleed valve. When the pressure within the combustion chamber reaches a certain level, the bleed valve is opened and a portion of the fluid within the combustion chamber is permitted to exit the combustion chamber. The removal of a portion of the fluid in the combustion chamber reduces the pressure within the chamber. A disadvantage of this process, however, is that the energy of the fluid bled from the chamber is lost. One alternative process is to feed the bled fluid through a turbine of a turbocharger. In this manner, some of the energy in the fluid is used to increase the boost in the engine. However, there is a need for an engine that can capture more of the energy from the excess pressure within the combustion chamber. Such an engine would be beneficial for use not only with HCCI technology, but also in any other application in which excess pressure is produced within the combustion chamber.